Measurement units are standards for measurement of physical properties or qualities. Every unit is related to a particular kind of property. For instance, the meter unit is uniquely related to the length property. Under our ontological approach, units are abstract spaces used as a reference metrics for quality spaces, such as physical qualia, and they are counted by some number. For instance, weight-units define some quality spaces for the weight-quality where specific weights of objects, like devices or persons, are located by means of comparisons with the proper weight-value of the selected weight-unit.

Evaluation results

It is obvious that not all the pitfalls are equally important; their impact in the ontology will depend on multiple factors. For this reason, each pitfall has an importance level attached indicating how important it is. We have identified three levels:

Critical

It is crucial to correct the pitfall. Otherwise, it could affect the ontology consistency, reasoning, applicability, etc.

Important

Though not critical for ontology function, it is important to correct this type of pitfall.

Minor

It is not really a problem, but by correcting it we will make the ontology nicer.

Relationships and/or attributes without domain or range (or none of them) are included in the ontology. There are situations in which the relation is very general and the range should be the most general concept "Thing". However, in other cases, the relations are more specific and it could be a good practice to specify its domain and/or range. An example of this type of pitfall is to create the relationship "hasWritten" in an ontology about art in which the relationship domain should be "Writer" and the relationship range should be "LiteraryWork". This pitfall is related to the common error when defining ranges and domains described in [3].

This pitfall appears when a relationship (except for the symmetric ones) has not an inverse relationship defined within the ontology. For example, the case in which the ontology developer omits the inverse definition between the relations "hasLanguageCode" and "isCodeOf", or between "hasReferee" and "isRefereeOf".

The contents of some annotation properties are swapped or misused. An example of this type of pitfall is to include in the Label annotation of the class "Crossroads" the following sentence ���the place of intersection of two or more roads���; and to include in the Comment annotation the word 'Crossroads'.

[5] Archer, P., Goedertier, S., and Loutas, N. D7.1.3 – Study on persistent URIs, with identification of best practices and recommendations on the topic for the MSs and the EC. Deliverable. December 17, 2012.